Synthesis and structural characterization of modified chitosan via acetylation and benzoylation

Chitosan is a derivative of chitin composed of glucosamine and N-acetyl glucosamine. It consists of functional groups including hydroxyl (OH) and amino (NH2) groups that allow for chemical modifications. However, its application is limited by poor solubility in most organic solvents. This study aimed to synthesize chitosan derivatives that might improve the solubility in organic solvents. The acetylation and benzoylation are applied for the structure modification. In this study, the modified chitosan was synthesized by chemical modification and the resulting physicochemical changes were characterized. Chitosan powder was modified through acetylation by reacting with acetic acid and acetic anhydride at 50-60ºC for 6-8 hours. The mixture was neutralized with NaOH, precipitated with cold 75% ethanol, filtered, and dried. Characterization was performed using FTIR. Benzoylation is the second step, involving the addition of benzoyl chloride after the initial acetylation. Sodium bicarbonate is added to neutralize hydrochloric acid byproduct, and maintain the pH. Solubility tests using distilled water, ethanol, chloroform, diethyl ether and toluene were done for the synthesized product. From the FTIR spectrum of unmodified chitosan, the amide band (1200-1700 cm⁻¹) was not sharply seen. Post-acetylation, FTIR confirmed successful chemical modification and the introduction of acetyl groups onto the amino sites. New absorption bands appeared around 1500-1600 cm⁻¹, confirming the formation of secondary amide. Meanwhile, in benzoylated chitosan, a peak around 1600-1650 cm⁻¹ associated with C-O stretching of ester groups and C=C stretching of aromatic ring. This confirmed substitution of benzoyl group in chitosan backbone. The study successfully demonstrated the synthesis of acetylated and benzoylated chitosan derivatives, confirmed by FTIR analysis and solubility test.